OK, here is an update. I figured out where the noise was coming from by accident.

Anyway, I heard the noise again today. So I was parking and not quite completely stopped and pulled up on the parking brake. I heard the noise so knew it wasn't my front brakes. I doubt they were ever the issue with this sound. Anyway, I repeated pulling the parking brake while moving slowly and that is definitely where the sound is coming from. I cannot imagine the rear brakes being worn out. The front brakes I replaced really didn't look that bad. I do lots of gravel road driving and sometime the low water crossings around here are gravely and muddy. Do I need to remove the drums and spray the assembly with the pressure washer? This might remove grease from the brake hardware and wheel bearings. How about compressed air?

Conor